Molecules, Biodiversity, Food and Health ALM June 2010

26 Pages·2010·0.21 MB·English

Molecules, Biodiversity, Food and Health
Biological Molecules
Biological Molecules
(a) describe how hydrogen bonding occurs between water molecules, and relate this, and other properties of
water, to the roles of water in living organisms;
Water is a polar molecule. This is because the oxygen atom pulls the shared electrons towards it,
meaning that water is slightly negatively charged at the oxygen and positively charged at the
hydrogen ends, so they can form hydrogen bonds with each other. This are continuing breaking and
reforming, so the molecules can move around.
Property of water Importance Examples Hydrogen bonds
Solvent Metabolic processes in all 70-95% of cytoplasm is If the solute is slightly
organisms rely on chemicals water. Dissolved chemicals charged or ionic, they will
being able to react together take part in processes such as interact with water
in solution respiration and molecules. The water
photosynthesis in living molecules will cluster around
organisms the charged parts, keeping
solute molecules apart
Liquid The movement of materials Blood in animals and the Water remains liquid over a
around organisms, both in vascular tissue in plants use large temperature range and
cells and on a large scale in water as a liquid transport can act as a solvent for many
multicellular organisms medium chemicals
requires a liquid transport
medium
Cohesion Water molecules stick to Transport of water in the A drop of water on the waxy
each other creating surface xylem relies on water surface of the leaf looks
tension at the water surface. molecules sticking to each almost spherical- it hardly
Cohesion also makes long, other as they are pulled up wets the leaf at all. This is
thin water columns very the xylem in the transpiration because hydrogen bonds pull
strong and difficult to break stream the water in at the surface.
This is cohesion, which also
Some small organisms make results in surface tension
use of surface tension to
‘walk on water’
Freezing Water freezes, forming ice on Organisms such as polar Water is unusual because its
the surface. Water beneath bears live in an environment solid form is less dense than
the surface becomes of floating ice packs. its liquid form. As water
insulated and less likely to cools, its density increases
freeze Lakes tend not to freeze until the temperature drops
completely, so aquatic to 4˚C, the density increases
organisms are not killed as again, so ice floats on water.
temperatures fall
Thermal stability Large bodies of water have Oceans provide a relatively The hydrogen bonds in liquid
fairly constant temperatures. stable environment in terms water restrict the movement
of temperature of the water molecules, so a
Evaporation of water can relatively large amount of
cool surfaces by removing Many land-based organisms water is needed to increase
heat. use evaporation as a cooling the temperature of water
mechanism, for example in
panting or sweating The evaporation of water
uses a relatively large
amount of energy, so water
evaporating from the surface
‘removes’ heat energy from
the surface
Metabolic Water takes part as a Water molecules are used in
reactant in some chemical hydrolysis reactions and in
processes the process of
photosynthesis

(b) describe, with the aid of diagrams, the structure of an amino acid;
H N-CHR-COOH
2

ALM June 2010
Molecules, Biodiversity, Food and Health
(c) describe, with the aid of diagrams, the formation and breakage of peptide bonds in the synthesis and
hydrolysis of dipeptides and polypeptides;
Synthesis
The –OH from one amino acid and the –H from the –COOH from the other are removed to
make water, and the C and the N join together via a peptide bond (CONH)
Hydrolysis
A water molecule is used to break the peptide bond. The –H joins back to the N, and the –
OH back to the C
(d) explain, with the aid of diagrams, the term primary structure;
The sequence of amino acids found in a protein molecule
(e) explain, with the aid of diagrams, the term secondary structure with reference to hydrogen bonding;
The coiling or folding of parts of a protein molecule due to the formation of hydrogen bonds formed
at the protein is synthesised. The main forms are the α-helix and the β-pleated sheet.
(f) explain, with the aid of diagrams, the term tertiary structure, with reference to hydrophobic and
hydrophilic interactions, disulfide bonds and ionic interactions;
The overall three-dimensional structure of a protein molecule. It is the result of interactions
between parts of the protein molecule such as hydrogen bonding, formation of disulfide bridges
and hydrophobic interactions
(g) explain, with the aid of diagrams, the term quaternary structure, with reference to the structure of
haemoglobin;
Protein structure where a protein consists of more than one polypeptide chain. Haemoglobin has a
quaternary structure as it is made up on four polypeptide chains.
(h) describe, with the aid of diagrams, the structure of a collagen molecule;
Made up of three polypeptide chains, each about 1000 amino acids long, wound around each other.
Hydrogen and covalent bonds (cross links) form between the chains. The cross links are staggered
to make the molecule stronger.
(i) compare the structure and function of haemoglobin (as an example of a globular protein) and collagen (as
an example of a fibrous protein);
Haemoglobin Collagen
Globular protein Fibrous protein
Soluble in water Insoluble in water
Wide range of amino acid constituents in primary Approx. 35% of the molecule’s primary structure
structure is glycine
Contains a prosthetic group- a haem Does not have a prosthetic group
Much of the molecule is wound into alpha-helix Much of the molecule consists of left-handed
structures helix structures

(j) describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a
monosaccharide carbohydrate;

(k) state the structural difference between alpha- and beta-glucose;
In α-glucose the –OH on carbon 1 is below the plane of the ring. In β-glucose it is above the chain of
the ring.
(l) describe, with the aid of diagrams, the formation and breakage of glycosidic bonds in the synthesis and
hydrolysis of a disaccharide (maltose) and a polysaccharide (amylose);
Disaccharide
Formation
Water is eliminated as the –OH from one glucose and the –H from an –OH from
the other leave. This means that the remaining O joins to the C on the other
glucose making a disaccharide
Breaking
Water is used to break the glycosidic bond between the subunits. The –H returns
to the O and the –OH returns to C
4
In polysaccharides, there are many glucose subunits joined together by 1,4-glycosidic bonds.
ALM June 2010
Molecules, Biodiversity, Food and Health
(m) compare and contrast the structure and functions of starch (amylose) and cellulose;
Amylose
Made up of α-glucose
Straight chain
Tends to coil up
Plant storage polysaccharide
Cellulose
Made up of β-glucose
In a chain, alternate glucose subunits are inverted
Forms straight chains
The β-glycosidic bond can only be broken down by a cellulose enzyme, which herbivors
have, but humans do not
Forms plant cell walls
(n) describe, with the aid of diagrams, the structure of glycogen;
Mostly like amylase, as in it has many 1-4 glycosidic bonds, but there are 9% 1-6 branches.
(o) explain how the structures of glucose, starch (amylose), glycogen and cellulose molecules relate to their
functions in living organisms;
Glucose
Simplists sugar. Used in respiration
Amylose
Insoluble in water so does not affect the water potential of the cell
Glycogen
Because it is so highly branched it can be broken down the glucose very quickly
Cellulose
Hundreds of the polypeptide chains lie side by side forming hydrogen bonds with each
other- very strong
The arrangement of macrofibrils in cell wells:
allows water to move in and out easily
determines how a cell can grow or change shape
Cell walls can be reinforced with other substances to provide extra support, or make the
walls waterproof
(p) compare, with the aid of diagrams, the structure of a triglyceride and a phospholipid;
Triglyceride
Glycerol plus three fatty acids
Phospholipid
Glycerol plus two fatty acids and a phosphate group
(q) explain how the structures of triglyceride, phospholipid and cholesterol molecules relate to their functions
in living organisms;
Triglyceride
Compact energy store
Insoluble in water
Does not affect cell water potential
Phospholipid
Part hydrophilic, part hydrophobic, so ideal basis for cell surface membranes
Cholesterol
Small, thin molecules that can fit into the lipid bilayer giving strength and stability
(r) describe how to carry out chemical tests to identify the presence of the following molecules:
protein (biuret test),
If present, turns from pale blue to lilac
Reducing sugars (Benedict’s test),
Add Benedict’s, heat to 80˚C. From Blue to orange-red
Non-reducing sugars (Benedict’s test),
If Reducing sugars test is negative, boil with hydrochloric acid, cool and neutralise with
sodium hydrogencarbonate. Repeat Benedict’s test.
starch (iodine solution)
Turns from yellow to blue-black if starch is present
lipids (emulsion test);
Mix the ethanol
Pour into water
If an emulsion forms, a lipid is present
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Molecules, Biodiversity, Food and Health
(r) describe how the concentration of glucose in a solution may be determined using colorimetry
Benedict’s test reveals the presence of reducing sugars
It results in an orange-brown precipitate
The more reducing sugar there is present, the more precipitate will be formed and the
more Benedict’s solution will be ‘used up’. If the precipitate is filtered out, the
concentration of the remaining solution can be measured
This will tell you how much Benedict’s solution has been used up, and this can be used to
estimate the concentration of reducing sugar in the original sample
Zero the device using a cuvette containing a ‘blank’- usually water
Prepare a calibration curve by
Taking a range of known concentrations of reducing sugars
Carry out Benedict’s test on each one then filter the precipitate out of each solution.
Use a calorimeter to give readings of the amount of light passing through the solutions
Plot the readings on a graph to show % transmission against concentration
Measure the % transmission of the unknown in the calorimeter
Use this to read the equivalent reducing sugar concentration from the % transmission
Nucleic acids
(a) state that deoxyribonucleic acid (DNA) is a polynucleotide, usually double stranded, made up of
nucleotides containing the bases adenine (A), thymine (T), cytosine (C) and guanine (G);
(b) state that ribonucleic acid (RNA) is a polynucleotide, usually single stranded, made up of nucleotides
containing the bases adenine (A), uracil (U), cytosine (C) and guanine (G);
(c) describe, with the aid of diagrams,
how hydrogen bonding between complementary base pairs (A to T, G to C) on two antiparallel DNA
polynucleotides leads to the formation of a DNA molecule,
There are two types of nucleotide bases- pyramidines and purines. They always pair up
together, with the purine Adenine always with the pyramidine Thymine, and the purine
Guanine always with the pyramidine Cytosine. There are two hydrogen bonds between A
and T, and three between G and C.
The strands are antiparallel because they run in opposite directions- the sugars are
pointing in opposite directions.
and how the twisting of DNA produces its ‘double-helix’ shape;
The antiparallel chains twist like a rope ladder to form the final structure- a double helix.
(d) outline, with the aid of diagrams, how DNA replicates semi-conservatively, with reference to the role of DNA
polymerase;
The double helix is untwisted
The hydrogen bonds between the bases are broken apart and the DNa ‘unzips’ to expose the bases
Free DNA nucleotides are hydrogen bonded onto their exposed complementary bases
DNA polymerade catalyses the formation of covalent bonds between the phosphate of one
molecule and the sugar of the next
This continues all the way down the DNA until there are two identical strands
These are ‘proof-read’ by DNA polymerase to prevent mistakes
(e) state that a gene is a sequence of DNA nucleotides that codes for a polypeptide;
(f) outline the roles of DNA and RNA in living organisms (the concept of protein synthesis must be considered in
outline only).
Protein synthesis
The required gene can be exposed by splitting the hydrogen bonds that hold the double
helix together in that region
RNA nucleotides form a complementary strand (mRNA). This is a copy of the DNA coding
strand
The mRNA peels away from the DNA and leaves the nucleus from the nuclear pore
The mRNA attaches to a ribosome
Then tRNA molecules bring amino acids to the ribosome in the correct order, according to
the base sequence on the mRNA
The amino acids are joined together by peptide bonds to give a protein with a specific
tertiary structure
Enzymes
(a) state that enzymes are globular proteins, with a specific tertiary structure, which catalyse metabolic
reactions in living organisms;
(b) state that enzyme action may be intracellular or extracellular;

ALM June 2010
Molecules, Biodiversity, Food and Health
(c) describe, with the aid of diagrams, the mechanism of action of enzyme molecules, with reference to
specificity,
The active site of an enzyme is a specific shape, depending on the reaction that it catalyses,
meaning that other molecules won’t fit into the active site
active site,
The area on an enzyme to which the substrate binds
lock and key hypothesis,
The theory of enzyme action in which the enzyme active site is complementary to the
substrate molecule, like a lock and key
induced-fit hypothesis,
The theory of enzyme action in which the enzyme molecule changes shape to fit the
substrate molecule more closely as it binds to it
enzyme-substrate complex,
The intermediary formed when a substrate molecule binds to an enzyme molecule
enzyme-product complex
The intermediate structure in which product molecules are bound to an enzyme molecule
lowering of activation energy;
Enzymes reduce the activation enthalpy so the reaction can proceed at a much lower
temperature
(d) describe and explain the effects of
pH,
Low pH = lots of H+ ions
H+ ions have a positive charge
Either extreme of H+ ion concentration can interfere with the hydrogen and ionic bonds
holding the tertiary structure together.
The pH affects the charge of the amino acids at the active site, so the properties of the
active site change and the substrate can no longer bind
At high pH values, a –COOH group will dissociate to become a charged –COO-
group
temperature,
Up to a certain point, increasing temperature will increase the rate of reaction, as there
will be more collisions between enzymes and the substrate, and more of these collisions
will have the required activation enthalpy for the reaction to proceed.
But heat also makes the molecules vibrate. This puts strain on the inter-molecular bonds,
and some of the weaker bonds (hydrogen bond and ionic bonds) may break.
In enzymes there are large numbers of these bonds holding the tertiary structure, and
especially the active site, in place.
As the heat increases, more and more of these bonds are broken
The tertiary structure disintegrates further and further
The rate of reaction decreases
If enough of these bonds are broken, the entire tertiary structure will unravel and the
enzyme will stop working
This is not reversible and is known as denaturation
enzyme concentration
As enzyme concentration increases, the rate of reaction increases linearly as there are
more active sites are available, until the substrate concentration becomes a limiting factor
and the rate stops increasing
substrate concentration
As the substrate concentration rises, the rate of reaction rises because there are more
substrate molecules to react. At higher concentrations, all of the active sites become filled,
so the rate of reaction remains the same
on enzyme activity;

ALM June 2010
Molecules, Biodiversity, Food and Health
(e) describe how the effects of
pH,
A starch-agar plate is made up by mixing starch with agar. The mixture is poured into a
petridish and left to set. It forms a semi-rigid gel in the plate.
Cut wells into each plate using a cork borer
Into each well place the same volume of a different pH buffer solution
Into each well except one, place an identical volume of stock amylase solution
Into the well without the amylase, add an equal volume of distilled water as a control
Incubate for 24h in a dry oven at 35˚C
Flood the plate with an iodine solution and rise with water
Measure the diameter of the cleared zone- this gives an indication of how much substrate
has been turned into product
temperature,
Take samples of potato tissue (containing catalase) using a cork borer then stick into discs
of equal thickness
Place an equal number of discs in each of seven tissues and place one in each of a range of
water baths from 20-80˚C
Place an equal volume of pH 7 buffer and hydrogen peroxide into each of sever separate
test tubes and place one in each water bath. Allow to equilibrate.
Taking each in turn, add peroxide/buffer mixture to the potato discs, then fix a stopper
and a side arm into the tube. Close the clip.
As oxygen gas is produced in the reaction it pushes the water bubble along the side arm.
Time how long it takes for the bubble to move 5cm.
enzyme concentration
Use the reaction as before, but keeping the temperature constant, and instead having a
different number of potato discs in each test tube
substrate concentration
As before, but keeping the temperature and the number of potato discs the same and
changing the volume of hydrogen peroxide in each test tube
on enzyme activity can be investigated experimentally;
(f) explain the effects of competitive and non-competitive inhibitors on the rate of enzyme-controlled reactions,
with reference to both reversible and non-reversible inhibitors;
Competitive inhibitor molecules
Have a similar shape to that of the substrate molecule. This means that they occupy the
active site, forming enzyme-inhibitor complexes. These complexes do not lead to the
formation of products because the inhibitor is not identical to the substrate.
The level of inhibition depends on the concentrations of inhibitor and substrate. Where the
number of substrate molecules is increased, the level of inhibition decreases because a
substrate molecule is more likely than an inhibitor molecule to collide with the active site.
Most competitive inhibitors do not bind permamently to the active site. They bind for a
short period of time and then leave. Their action is described as reversible, as the removal
of the inhibitor form the reaction mixture leaves the enzyme molecule unaffected.
Non-competitive inhibitors
Do not compete with substrate molecules for a place in the active site. Instead, they attach
to the enzyme, molecule in a region away from the active site. The attachment of non
competitive inhibitors distorts the tertiary structure of the enzyme molecule, leading to
the shape of the active site changing. This means that they substrate no longer fits into the
active site so the enzyme-substrate complexes cannot form and the reaction rate
decreases.
The level of inhibition depends on the number of inhibitor molecules present. If there are
enough inhibitor molecules to bind to all of the enzyme molecules presend, then the
enzyme controlled reaction will stop. Changing the substrate concentration will have no
effect on this form of inhibition
Most non-competitive inhibitors bind permanently to the enzyme molecule. The inhibition
is irreversible, and any enzyme molecule bound by inhibitor molecules are effectively
denatured.
(g) explain the importance of cofactors and coenzymes in enzyme-controlled reactions;
Cofactors
Ions that increase the rate of enzyme-controlled reactions. Their presence allows enzyme-
substrate complexes to form more easily.
ALM June 2010
Molecules, Biodiversity, Food and Health
Coenzymes
Small, organic, non-protein molecules that bind for a short period of time to the active site.
They may bind just before, or at the same time, as the substrate binds. In many reactions,
coenzymes take part in the reaction, and like substrate, are changed in some way. Unlike
the substrate, coenzymes are recycled back to take part in the reaction again. The role of
coenzymes is often to carry chemical groups between enzymes so they link together
enzyme-controlled reactions that need to take place in sequence.
Some coenzymes are permanent parts of the enzymes- prosthetic groups. These contribute
to the shape of the enzyme.
(h) state that metabolic poisons may be enzyme inhibitors, and describe the action of one named poison;
Potassium Cyanide acts as a non-competitive inhibitor of the enzyme cytochrome oxidase, which is
involved in the oxidation of ATP. When this is inhibited, aerobic respiration cannot occur, and so
the organism can only respire anaerobically, which leads to a build up of lactic acid, toxic to the
cells.
(i) state that some medicinal drugs work by inhibiting the activity of enzymes

ALM June 2010
Molecules, Biodiversity, Food and Health
Food & Health
Diet & Food Production
(a) define the term balanced diet;
A diet that contains all the nutrients of the nutrients requires for health and growth.
(b) explain how consumption of an unbalanced diet can lead to malnutrition, with reference to obesity;
Malnutrition is caused by an unbalances diet. Obesity is called by consuming too much energy and
the excess energy is deposited as fat in the adipose tissues. Obesity is the condition in which excess
fat deposition impairs health and it usually defined when a person has a BMI
(BMI = Mass (kg) / (height (m) 2)) of 30 or over. This indicated a body weight of 20% or more above
the weight recommended for the height.

BMI Category
<18.5 Underweight
18.5-25 Healthy
25-30 Overweight
30-35 Obese (class I)
35-40 Obese (class II)
>40 Morbidly obese

(c) discuss the possible links between diet and coronary heart disease (CHD);
Excess salt in the diet decreases the water potential of the blood. As a result, more water is held in
the blood and blood pressure increases. This can lead to hypertension, which can damage the inner
lining of the arteries, which is one of the early steps in the process of atherosclerosis
Saturated fats can cause damage to the heart
45-47% of deaths from cholesterol have been linked to high blood cholesterol levels
(d) discuss the possible effects of a high blood cholesterol level on the heart and circulatory system, with
reference to high-density lipoproteins (HDL) and low-density lipoprotein (LDL);
Cholesterols are transported around the body in the form of lipoproteins.
High Density Lipoproteins
A combination of unsaturated fats, cholesterol and protein. They tend to carry cholesterol
from the body tissues to the liver, where the cholesterol is used to make bile or broken
down. Therefore, high levels of HDL are associated with reducing blood cholesterol levels.
They cal reduce deposition on the artery walls.
Low Density Lipoproteins
Produced by the combination of saturated fats, cholesterol and protein. They tend to carry
cholesterol from the liver to the body tissues. A high blood concentration of LDLs cause
dispositions on the artery walls.
Saturated fats decrease the activity of LDL receptors, so as the blood LDL concentration
rises; less is removed from the blood, resulting in higher concentrations of LDL in the
blood, which are then deposited on the artery walls.
(e) explain that humans depend on plants for food as they are the basis of all food chains. (No details of food
chains are required);
Plants can carry out photosynthesis to convert light energy to chemical energy. They also absorb
plants from the soil and manufacture a range of other biological molecules. Herbivores make use of
these biological molecules when they eat and digest food. Humans eat both plants and herbivores,
gaining our nutrition both directly and indirectly.
(f) outline how selective breeding is used to produce crop plants with high yields, disease resistance and pest
resistance;
A pair of plants which display the desired characteristics are allowed to reproduce. The offspring
produced are sorted carefully to select those with the best combination of characteristics and only
those offspring are allowed to reproduce. If this careful selection and controlled reproduction
continues for many generations, the required characteristic becomes more exaggerated.
e.g. Tomatoes have been bred with improved disease resistance
(g) outline how selective breeding is used to produce domestic animals with high productivity;
(h) A pair of animals which display the desired characteristics are allowed to reproduce. The offspring
produced are sorted carefully to select those with the best combination of characteristics and only
those offspring are allowed to reproduce. If this careful selection and controlled reproduction continues
for many generations, the required characteristic becomes more exaggerated.
e.g. chickens bred for eggs lay over 300 eggs a year, whereas their unselective relatives can
lay only 20-30
ALM June 2010
Molecules, Biodiversity, Food and Health
(h) describe how the use of fertilisers and pesticides with plants and the use of antibiotics with animals can
increase food production;
Fertilisers
Replace minerals in the soil which may have been removed by the previous crops. They
contain Nitrate, Phosphate and Potassium. They increase the rate of growth and the
overall size of crops
Pesticides
Kill organisms that cause diseases in crops. These organisms would reduce yield or kill the
crop. Many crops are sprayed with fungicides to reduce fungal growth in the leaves or
roots. Sheep are dipped to kill ticks.
Antibiotics
Infected animals can be treated with antibiotics to reduce the spread amongst animals that
are intensively farmed in close proximity to each other. Such diseases could reduce the
growth performance of the animals and may impair reproduction.
(i) describe the advantages and disadvantages of using microorganisms to make food for human
consumption;
Advantages
- Production of protein can be many times faster than that of animal or plant protein
- Production can be increased or decreased according to demand
- No animal welfare issues
- They provide a good source of protein for vegetarians
- The protein contains no animal fat or cholesterol
- Single-cell protein production could be combined with removal of waste products
Disadvantages
- Many people may not want to eat fungal protein that has been grown on waste
- The microorganisms are grown in huge fermenters and need to be isolated from the
material on which they grow
- The protein has to be purified to ensure it is uncontaminated
- The conditions needed to grow the useful organisms are ideal for pathogenic
organisms. Care needs to be taken to ensure that the culture is not infected
- The protein does not have the taste or texture of traditional protein sources
(j) outline how
salting,
Dehydrates any organisms as water leaves them by osmosis
adding sugar,
Dehydrates any organisms as water leaves them by osmosis
pickling,
Acid pH denatures any microorganism’s proteins and enzymes
freezing,
Retards enzyme activity so their metabolism, growth and reproduction is slow
heat treatment
Kills harmful organisms
irradiation
Kills organisms by disrupting their DNA structure
can be used to prevent food spoilage by microorganisms.

Health and disease
(a) discuss what is meant by the terms health and disease;
Health
A state of mental, physical and social wellbeing
Disease
A departure from good health caused by a malfunction of the mind or body
(b) define and discuss the meanings of the terms parasite and pathogen;
Parasite
An organism that lives on or in another living thing causing harm to its host
Pathogen
An organism that causes disease

ALM June 2010
Molecules, Biodiversity, Food and Health
(c) describe the causes and means of transmission of malaria, AIDS/HIV and TB (knowledge of the symptoms
of these diseases is not required);
Malaria
If the host already has malaria, the female anopheles mosquito will suck the parasite
gametes into its own stomach
The gametes fuse and the zygotes develop in the mosquito’s stomach
Infective stages are formed and these move to the mosquito’s salivary glands
When the mosquito bites another person, it injects a little saliva as an anticoagulant
The saliva contains the infective stages of the parasite
In the human host, the infective stages enter the liver where they multiply before passing
into the blood again
In the blood they enter red blood cells, where the gametes are produced
HIV/AIDS
The virus enters the body by
Exchange of bodily fluids such as blood to blood contact
Unprotected sexual intercourse
Unscreened blood transfusions
Use of unsterilised surgical equipment
Sharing hypodermic needles
Accidents such as ‘needlestick’
Across the placenta or during childbirth
From mother to baby during breastfeeding
It can remain unactive in the body for many years. Once the virus becomes active it attacks
and destroys T helper cells in the immune system, effectively rendering the immune
system useless
Tuberculosis
The bacteria are contained in the tiny droplets of liquids which are released when an
infected person coughs, sneezes or talks. But it takes close contact with an infected person
over a long period of time to contract the disease. There are a number of conditions which
make contraction and spread more likely
Overcrowding- many people eating and sleeping together in one house
Poor ventilation
Poor health- particularly if a person has HIV/AIDS
Poor diet
Homelessness
Living or working with people who are migrated from areas where TB is more
common
TB can also be contracted from the milk or meat of cattle.
(d) discuss the global impact of malaria, AIDS/HIV and TB;
Malaria
Kills about 3 million people annually
Affects about 300 million people
Currently limited to areas where the Anopheles mosquito can survive, which is currently
the tropical regions.
But, with global warming, the Anopheles mosquito may be able to survive further north,
even into parts of Europe.
HIV/AIDS
Spreading into pandemic proportions all over the world
Approximately 45 million people living with HIV/AIDS at the end of 2005
More than half of these are in Sub-Saharan Africa
About 5 million people infected each year
By the end of 2005, nearly 30 million people had died from HIV/AIDS related illnesses
It is thought that the number of people living with HIV/AIDS in China will soon exceed the
number in any other country
Tuberculosis
Approximately 1% of the population is infected every year, and 10-15% of those will go on
to develop the disease
In 2005 there were 8.8 million new cases of Tuberculosis and 1.6 million people died.
Up to 30% of the world’s population may be infected with TB

ALM June 2010